FIELD OF THE INVENTION
This invention relates to a method and apparatus for a reciprocating magnetic refrigerator. More particularly, a plurality of porous matrices of paramagnetic material are located in tandem within a single reciprocating displacer. Employment of, for example, two matrices effectively doubles the heat removal capabilities per cycle of the displacer. This invention thus provides a more continuous removal of heat energy from a heat source.
At either end of the displacement stroke, one matrix is in a maximum magnetic field of a superconducting magnet, while the other matrix is in a minimum, or essentially zero, field.
The magnet is encased in a magnetically soft material which contains the magnetic flux in a localized area. Encasing the magnet in this manner allows the matrices to be spaced closer to one another and reduces the length of stroke required to move the matrices from the high magnetic field region to the low magnetic field region. The displacer is located for reciprocating movement in a cylinder which is provided with separate ports and paths. A gas pump for low temperature is connected to one set of ports, and a high temperature gas pump is connected to the other set of ports. The gas pumps cause heat exchange with the paramagnetic material by forcing helium gas through the displacer and thus the paramagnetic material matrices. As the displacer moves the matrices between the two extremes of the magnetic field the gas flow is momentarily interrupted to prevent heat exchange from occurring.